Apparatus removing metallic particles from effluent liquid waste

ABSTRACT

An apparatus for separating solid particles from the suction effluent of, for example, a dental office, preferably driven by a dental office vacuum pump, includes a surge tank for accommodating effluent overfill connected to a sedimentary deposit tank for sedimentation of effluent particles. A bypass conduit is connected to the surge tank inlet which is equipped with a vacuum break valve for allowing air into the system when the suction openings are closed. The sedimentary deposit tank has a series of baffle chambers through which effluent flows in sequence, and in each of which chambers sediment is deposited for later removal. The surge tank preferably has a liquid level sensor and warning device. Modular filters or adsorbants may be installed in the sedimentary deposit tank, or a modular auxiliary filter may be connected downstream of the tank. Chemical injection may be used to improve sedimentation. A positive air pressure source or auxiliary pumps may be used to drive the effluent, particularly in large installations incorporating multiple surge and deposit tanks. Full tank effluent removal and drying facilities are optionally provided.

RELATED APPLICATION DATA

The present patent application is a continuation-in-part of pending USpatent application Ser. No. 09/768,848 filed on Jan. 23, 2001, that is acontinuation-in-part of PCT International Patent Application No.PCT/CA99/00665 filed on Jul. 21, 1999 that designates the United Statesand that claims priority from Canadian patent application No. 2,243,580,filed on Jul. 21, 1998.

FIELD OF THE INVENTION

This invention relates to methods and apparatus suitable to removeparticles from effluent waste, and particularly, to remove amalgam andother metallic particles and other abrasive solids from dental officesuction effluent.

BACKGROUND OF THE INVENTION

Although amalgams are less frequently used for new dental fillings thanwas the case some decades ago, nevertheless, amalgams continue tocomprise a significant portion of the metallic particle component ofdental office effluent because of the fact that old fillings comprisingamalgams are drilled out and removed in the effluent waste when newfillings are effected to replace the old. Further, even under currentdental practice, an amalgam is preferred for some tooth fillingsituations. The use of an amalgam in a filling is never a 100% efficientprocess; amalgam residues are discharged into the dental officeeffluent. Typically, dental amalgam comprises a number of metals,invariably of course including mercury and almost always at least somesilver. Because mercury is a poison that can accumulate in livingtissues and can pose a health hazard to species in a food chain exposedto mercury-containing compounds, and since humans are inevitably at theend of the food chain, it follows that effluent containing amalgams canpose a health hazard to the community at large. Also, certain metalssuch as silver are commercially valuable if recovered in quantity. Forthose reasons, it is desirable to devise apparatus and processes forremoving amalgams from dental office effluent. In addition to removingamalgams, other matter disposed into dental office suction effluentincludes aluminum oxides used in air abrasion treatments and other solidwaste material. These solid materials tend to wear out or damage vacuumpumps and other equipment downstream of the dental chair suctionapparatus, and also constitute effluent water contaminants. Therefore,it is desirable for the apparatus to remove solid abrasive material andother particulate waste from the dental office suction effluent.

Previously known apparatus for removing amalgam particles from dentaloffice suction effluent are known to include a collecting tank forcollecting a working day's accumulation of suction effluent from one ormore sources of such waste. The waste is sucked from the dental chairsuction apparatus and into the collecting tank by a vacuum pump. Whenthe vacuum pump is turned off, an outlet valve is opened and theaccumulated waste is deposited into a separation device intended toseparate metal particles from the effluent liquid. Flow into theseparation device is induced by the head of fluid in the collectingtank. Particles passing through the separation device are separated fromthe waste by gravity and settle to the bottom of the separation device.The flow rate is dependent on the head inside the collecting tank; asthe head diminishes, the flow rate also diminishes. The changes in flowrate are undesirable because the particle separation rate is affected,and the system becomes prone to plugging when the flow rate decreases.Also, since the waste can be deposited only when the vacuum pump is off,waste is usually moved to the separation device at the end of the day.As a result, the collecting tank and separation device tend to beundesirably large.

Another known apparatus is a centrifuge type system that separatesheavier metal particles from effluent liquid by collecting the particlesat the peripheral wall of the centrifuge. This apparatus does noteffectively separate lighter particles, and is expensive to purchase andoperate due to the complexity of its mechanical parts.

Yet another known apparatus uses a dedicated mechanical pump to suctionwaste liquids through a separator device. Again, a dedicated pump can beexpensive to purchase and to maintain, and can be undesirablyspace-consuming.

Such known systems can become quite complex, unwieldy and expensive, asfor example that disclosed in Rails U.S. Pat. No. 5,885,076 granted Mar.23, 1999. Rails teaches the use of sedimentation, co-precipitation andfiltration in an expensive complicated apparatus that is probablyeconomical, if at all, only for relatively large installations such as amilitary base dental complex.

An alternative approach described in Ludvigsson U.S. Pat. No. 5,205,743granted Apr. 27, 1993 involves provision of an air flow in the vicinityof the patient's mouth and suction from that air flow; such apparatus isdesigned to remove mercury vapour present in the air flow.

The present invention overcomes some of the shortcomings of the priortechnology and achieves further advantages that will be apparent afterreviewing the following summary of the invention and detaileddescription.

SUMMARY OF THE INVENTION

According to the invention, an apparatus is provided for removingmetal-containing particles and other waste particles from effluent,particularly effluent from a dental office. While herein the term “metalparticles” will frequently be employed, it is contemplated that theapparatus is fully capable of separating other solid particles fromeffluent liquid. Further, with the aid of one or more precipitants,selected solutes may also be removed. In a particular application to bedescribed in detail, effluent from a dental office suction apparatus isdiscussed; the metal particles are primarily amalgam particles made ofmercury and silver alloyed together in an amalgam composition, sometimeswith other metals. The metal particles may be in solid particulate formsuspended in the liquid, or may be in solute form dissolved in theliquid. The solid particles other than amalgam residues include aluminumoxides used in air abrasion treatment, enamel and dentin from teeth,porcelain, acrylic used in bridges, and prosthetic cementing agents suchas zinc phosphate cement used in crowns and bridges. These solidparticles are typically suspended in the liquid effluent. Herein suchparticles are sometimes collectively referred to as “target particles”,since they are targeted for removal from the effluent. Such targetparticles also include precipitated particles obtained in the effluentsuspension by precipitation of solutes out of solution.

According to one aspect of the invention, an apparatus for removingmetal particles and other solid particles from liquid suction effluentcan be installed in a dental office using a pre-existing suction/vacuumpump system to provide fluid flow through the apparatus, withoutrequiring dedicated fluid-flow provenance devices. The apparatus mayshare a common vacuum pump with conventional dental chair suctionapparatus, without interrupting the use of suction equipment at thedental chairs.

Removal of solid particles from liquid suction effluent may be effectedby a combination of sedimentation and filtration, assisted byflocculation and precipitation. The invention is not concerned with thespecific choice of sedimentary deposit apparatus, a preferredimplementation being presented herein as a suitable exemplification ofsuch apparatus. Nor is the invention concerned with specific choices ofprecipitants, coagulants, flocculants, or other associated materials toeffect or facilitate removal of solids or solutes; rather, the inventionis concerned with the overall system of solids removal, the provision ofapparatus and methods for controlling flow of liquids and gases therein,and the facilitation of removal and replacement of deposit tanks thathave been filled with solid waste.

In accordance with a preferred embodiment of the invention, the dentaloffice suction effluent is passed from dental chair suction equipmentoutlets to a surge tank via a suitable inlet port for the surge tank.The surge tank in turn passes effluent into a sedimentary deposit tank,closed on all sides when in use and preferably readily detachable foremptying and replacement. The sedimentary deposit tank in a preferredembodiment has a series of interior walls that separate the interior ofthe sedimentary deposit tank into a consecutive series of bafflechambers, including an inlet baffle chamber at the beginning of theseries and an outlet baffle chamber at the end of the series. The inletbaffle chamber receives effluent through an inlet port, situated in thepreferred embodiment in the lid of the sedimentary deposit tank. Thebaffle chambers in between the inlet and outlet baffle chambers each inturn receive effluent passed to such chamber by the preceding suchbaffle chamber in the series. So, liquid effluent flows from the inletbaffle chamber through the interconnected series of baffle chambers tothe outlet baffle chamber from whence it passes via a deposit tankoutlet port, and preferably thence to an auxiliary filtration unit, aswill be further described below.

In such preferred sedimentary deposit tank, each baffle chamber, or atleast some of them, receive removable baffles composed of inverseV-shaped strips, inclined either in one dimension, resembling a chevron,or in two dimensions, resembling a gable in appearance. Such baffles arearranged and joined to form channels bounded above and below by thebaffle or sedimentary tank surfaces and the side walls of which areformed by the interior divider walls of the baffle chamber into whicheach baffle is individually inserted. Further, the transverse width ofeach baffle must be less than the transverse width of the sedimentarydeposit tank such that after the insertion and centering of the baffleinside the corresponding baffle chamber, there are apertures between theside walls of the sedimentary tank and the edges of the baffles to allowfor the effluent to access and exit the channels formed by the bafflesand baffle chamber walls.

In a preferred embodiment of the invention designed to minimizemanufacturing costs, the baffles in the baffle chambers are individuallyformed, configured and dimensioned so that they can be verticallystacked on top of each other or aligned end to end within the bafflecompartment. In another preferred embodiment of the invention designedto minimize the costs of assembling sedimentary tank equipment, severalvertically spaced baffles are integrally formed as a unit, theconfiguration and dimensions of such integral baffle units and thebaffle compartments selected so that just one integral baffle unit fitsinto each compartment. Such chevron or gable-shaped baffles ormulti-surface integral baffle units can be cheaply and easilymanufactured in quantity and simply inserted into a mating bafflecompartment without requiring any fasteners, and removed just as easilyfor cleaning or replacement. In a further embodiment of the inventionthat provides for additional effluent flow paths through an individualbaffle chamber thus promoting efficient sedimentation, two sets ofinclined baffle surfaces, each of approximately half the width of anindividual baffle chamber, may be fixedly attached on opposite sides ofa vertical dividing wall to provide a single unit that can be removablyinserted into a compartment of the sedimentary deposit tank.Alternatively, in the interest of modular design, baffle surfaces may befixedly attached to the baffle chamber walls, such walls being designedto be easily removable from the sedimentary deposit tank for cleaning orreplacement of the fixedly attached baffle surfaces.

Each transverse baffle chamber wall of the preferred sedimentary deposittank separating each baffle chamber from its neighbouring chamber orchambers, extends from the floor of the chamber to a top edge of thechamber and has a notch on its top edge. The bottom edge of each notchis positioned on a pass-over height that is common to all of thechambers. As described above, the water successively enters, passesthrough the baffle channel and exits each baffle chamber; accordingly,for the baffle chamber to be functional, the horizontal position of theopenings (comprising notches and inlet and outlet ports) in each twoneighboring chambers must alter in transverse position, so the fluid canenter each chamber on one side, pass through the channel formed by thebaffle and exit the chamber on the other end. Because all the notches inone sedimentary deposit tank are preferably at the same vertical level,the second baffle chamber (the neighbour to the inlet baffle chamberimmediately downstream thereof) can receive liquid only when the inletbaffle chamber is full and liquid passes over the notch on theintervening transverse baffle chamber wall once it has reached thepass-over height. Similarly, liquid can pass from the second bafflechamber to the third only after the second baffle chamber is full andliquid passes over the notch on top of the wall of the second chamber atthe pass-over height to enter the third baffle chamber, and so forth upto the final outlet baffle chamber. When the outlet chamber becomesfull, it passes liquid out of the sedimentary deposit tank via theoutlet port. In a preferred embodiment of the present invention, thebaffle chamber walls are integrally formed as a fixed part of thesedimentary tank structure. Alternatively, however, the baffle chamberwalls may be separately formed and removably configured to engage slotsin the walls and floor of the sedimentary deposit tank, the slotsholding such baffle chamber walls in place inside the sedimentarydeposit tank. Optionally, inclined baffle surfaces may be fixedlyattached to such removable baffle chamber walls, as mentioned above.

In each baffle chamber, the target particles, being on the averageheavier than the liquid effluent, will tend to sink to the bottom of thebaffle chamber. Those target particles that are not collected in thefirst baffle chamber have a chance to be collected in the second, and soon in sequence to the final outlet baffle chamber, so that overall thereis a good chance that at least the heavier target particles will becollected at the bottom of the various baffle chambers. Further particleseparation can be effected by passing the suction effluent through aplurality of screens or filters positioned in some of the bafflechambers. In a preferred embodiment of the invention, such screens orfilters may be located in the final (downstream) baffle chamber or finalfew baffle chambers to remove particles remaining in the effluent aftersedimentation in upstream baffle chambers has taken place beforeeffluent exits the sedimentary deposit tank. Removal of dissolved solutemetal particles from the effluent liquid can be achieved by adding asuitable chemical agent such as a precipitant, chelating agent orcoagulant, or some combination thereof to the effluent being processedin the sedimentary deposit tank, such chemical agent(s) being selectedfor combination with solute mercury or silver or both, it being animportant objective to remove solute mercury particles, and an objectivealso to remove solute silver particles from the effluent. The chemicalagent precipitates out of the solution metal particles that are insolute form and may facilitate formation of larger particles fromsmaller particles. Among suitable such agents are precipitants such aspotassium iodide (KI), potassium iodate (KIO₃), sodium sulfide (Na₂S)and various other sulfur compounds; a preferred chelating agent issodium ethylenediaminetetraacetic acid (sodium EDTA).

The chemical agent(s) may conveniently be injected into the effluentbeing processed in the sedimentary deposit tank by means of one or moreinlet ports preferably located at or near the top of the second or thirdbaffle chamber so that after the largest particles have settled out ofsolution in the first or second baffle chambers, the chemical agent(s)may act on the entirety of the liquid passing through the remainingdownstream baffle chambers in sequence.

If desired, a time-dependent delivery apparatus may provide a meteredamount of chemical agent via one or more inlet ports to the second orthird baffle chamber, or the chemical agent(s) may be added on aflow-rate-dependent basis, as preferred. The amount of agent added perunit of time or per unit of effluent flow will be dependent in part uponthe chemical characteristics of the agent(s) employed, and in part uponthe expected concentration of particles in the effluent liquid, and isusually best determined empirically. Accordingly, the amount of chemicalagent added to the settlement tank baffle chamber per unit of time orper unit of effluent passing through the baffle chamber is preferablyadjustable. According to one aspect of the invention, the introductionof such chemical agent(s) is automatically regulated to occur only whenthe dental office suction apparatus is operating actively; an overnightshutdown will occur without intervention.

As an alternative to or in combination with the addition of chemicalagents such as precipitants, flocculants and chelating agents to theeffluent, an adsorbent compound may be used to remove metal ions fromsolution by surficial adsorption. Such a compound may be incorporated inthe construction of the interior of the system settlement tank wherebymetal ions dissolved in the effluent passing through the tank areadsorbed by the adsorbent material. A preferred adsorbent material isbentonitic clay. In a preferred embodiment of the present invention,finely divided bentonite clay particles are combined with activatedsilica particles and enclosed in a porous and permeable membrane,similar in function and appearance to a tea bag. Such bentonite andsilica filled membrane may preferably be located in the final few bafflechambers of the sedimentary deposit tank whereby dissolved mercury andother metal ions may be adsorbed by the bentonite, and organic compoundsmay be adsorbed by the silica prior to the effluent exiting the tankthrough the tank exit port.

In order to control the growth of bacteria, yeasts, molds, fungi andviruses in the effluent treatment system, a disinfectant is added to theeffluent at the individual operatory suction openings. In the preferredembodiment of the invention, the disinfectant is chlorine, bromine orperoxide based, and utilized in a solid dissolvable form.

The flow rate at which the effluent passes through the individual bafflechambers in the sedimentary deposit tank is an important feature of thesolid removal system. Precisely, it is desirable to have as slow a flowrate of effluent as possible, to maximize the time for the particles toseparate from the effluent in the sedimentary deposit tank. The flowrate of effluent through the sedimentary deposit tank is preferablymaintained at a relatively constant value and may be regulated to thisend. However, the flow rate may be changed if, for example, the surgetank becomes backed up with effluent. A typical dental office disposesof about one liter of suction effluent per chair per working day, butthis quantity may be higher if a cuspidor drain is also connected to thesuction apparatus (which may be desirable in the interest of preventingadditional undesirable mercury-containing particles from entering theecosystem, although it is undesirable in that it will typically requirea larger-sized separation apparatus to handle the larger volume ofeffluent). The optimal flow rate setting can be estimated empirically asbeing equal to the total volume of effluent generated during a dutycycle (for example an 8 hour working day), divided by the totalavailable time for operating the sedimentation system per duty cycle,the resulting rate multiplied by an appropriate safety factor (greaterthan 1.0) to guard against backup of the system to give the optimal flowrate. For this purpose, the elements of the apparatus according to theinvention are suitably selected for dimensions, capacity, vacuum level,etc. (this may be done empirically). In particular, the conduitconnected to the sedimentary deposit tank outlet may be sized so as toconstrict the flow of liquid effluent. As well, the conduit between thesurge tank effluent outlet and the sedimentary deposit tank inlet may besized so as to constrict the flow of liquid effluent. As well, athrottle valve or other suitable flow regulator such as a needle valvemay be installed to control the rate of outflow from the sedimentarydeposit tank. A flow meter may also be included to measure the flow rateof effluent exiting the sedimentary deposit tank and display the flowrate measured, permitting the operator to adjust the flow by adjustmentof the throttle valve. While alternative automatic or semi-automaticfeedback control of the flow can be devised, it would be expected to addappreciably to the cost of manufacture of the equipment.

Although the sedimentary deposit process is effective to remove asatisfactorily high proportion of the target particles desired to beremoved from the effluent, the sedimentary deposit tank desirablyincludes an outlet screen filter in the final baffle chamber to catchany floating materials as well as any other materials that did notsettle out in the upstream baffle chambers. Downstream of thesedimentary deposit tank, an auxiliary filtration unit to filter outfiner solids may be provided, and a mercury vapour filter may beprovided in the air bypass conduit. In the preferred embodiment of theinvention, the auxiliary filtration unit is incorporated into theconstruction of the sedimentary deposit tank and may be located in thefinal baffle chamber of the tank.

Desirably, at least the sedimentary deposit tank and optionally variousfiltration units may be connected to the system as removable modularunits, or if the filtration unit is desired to be removed independentlyof the sedimentary deposit tank, each of the sedimentary deposit tankand filtration unit may be devised as removable modular units. Forheavier volume effluent processing, two or more sedimentary deposittanks may be coupled into the system in parallel or in series. It isexpected that modular design will be most efficacious for dental officesbecause it is not to be expected that dentists or their staff will beeffectively able to remove deposited sediment from the sedimentarydeposit tank nor remove accumulated particle residues from thefiltration unit. It is desirable that such removal be done by acompetent effluent residue processing facility. Therefore, it isexpected to be preferred that the modular sedimentary deposit tankand/or filtration unit be removed periodically and replaced by freshsuch tanks or units from time to time as required. The spent tank orunit with an accumulation of metallic particles can then be sent to aprocessing facility for removal of the metallic particles, possiblychemical separation of mercury from silver, etc., and cleaning of themodular units for re-use. However, if, in any particular installation,it is desired instead that onsite removal of particles be effected, thensuitable bypass valves should be provided at the appropriate fluid flowports, and means provided for removal of particles (e.g. for thesedimentary deposit tank, the entire top wall might be opened orremoved, and for the filtration chamber, an access door provided topermit replacement of filters and removal of particles, etc., accordingto the designer's preference).

Further, according to another aspect of the invention, a fullsedimentation tank may be disconnected from active use, and connected toa suction attachment to transfer excess waste water from thesedimentation tank into the surge tank which waste water in turn isretreated in the replacement sedimentation tank. The full tank may thenbe coupled into a drying conduit connection for a period of time andexposed to tank-drying airflow to permit liquid in the tank to vaporizeand be removed in the air outflow. A dry tank is easier to handle bywaste processing service personnel than a tank containing a large volumeof liquid. Further yet, monitoring means may be provided to determinewhen the solids content of a sedimentary deposit tank has reached apredetermined level, so as to facilitate transfer of the effluent to apreviously idle sedimentary deposit tank.

For the apparatus to work to best advantage without dependence ongravity, a pressure differential must be maintained between the inletport of the surge tank and the outlet port of either the filtration unitor the outlet port of the sedimentary deposit tank if no filtration unitis present. To this end, the air pressure at the system outlet ismaintained at a level less than the air pressure at the system inlet.Assuming that the system operates by using a vacuum pump, the pressuresin question are below atmospheric pressure. The system requires that airenter the inlet either via the dental chair suction devices or via aseparate air inlet, preferably a vacuum break valve as described below.Consequently, in a vacuum system, the inlet pressure is nearer (butbelow) atmospheric pressure, while the downstream pressure at theseparator outlet is nearer the pressure drawn by the vacuum pump. Thispressure differential causes an overall flow of effluent fluid throughthe surge tank, into the sedimentary deposit tank, thence to theauxiliary filtration unit (if present), to exhaust via the separationsystem outlet into the vacuum pump exhaust line.

A vacuum pump may apply a partial vacuum at the system inlet port, whileat the system outlet port, the vacuum pump draws a higher vacuum, sothat there is a pressure differential sufficient to drive effluentliquid properly through the separator system. A pressure differential ofthe order of 3-10 kPa between inlet and outlet vacuum levels issufficient to cause liquid effluent to flow through a small simplesystem, but depending upon the pressure drops within the system, thesize of ports, passages, chambers, viscosity of the effluent, etc., thepressure differential may have to be higher. It is best, again, to takean empirical approach and permit the pressure differential to beadjusted manually to suit the user's requirements.

In order to maintain constant air flow through the apparatus when thevacuum pump is operating, there is a spring-loaded vacuum break valvethat opens when the suction apparatus openings from the dental chairsare all closed. (Depending upon the spring force exerted on the vacuumbreak valve, the valve will remain closed when the suction equipment ofone or more dental chairs operates, and the requisite input air to thesystem will be provided via the dental chair suction apparatus.) Whenthe vacuum break valve is opened, the top of the surge tank is open tothe ambient air, and suction through the apparatus is effected, causingfluid to flow through the apparatus.

The required air pressure differential between inlet and outlet caninstead be positively applied by an air pressure source, but in thatevent, some means must be interposed at the surge tank to prevent airpressure from driving effluent upstream. According to an aspect of theinvention, an additional regulator valve for the surge tank may beprovided to accommodate a positive air pressure. The positive airpressure is applied during intervals between successive active operationof the suction drainage system from dental chairs. As dental officesinvariably have a source of air under pressure, this source may be usedto provide a positive air pressure differential.

If the surge tank becomes full, overflow effluent is sucked through theair outlet port and discharged into the air bypass conduit, thence tothe vacuum pump draw line and thence eventually into the municipaldrain. However, it is desirable that the system should operate in such amanner as to avoid having the surge tank become completely full, sinceeffluent exiting through the air outlet port will contain particles thatwill not be separated by the separator. Even if a pinnacle filter or thelike catches some of these particles, solutes and some finer solidparticles would be expected eventually to be discharged into themunicipal drain. A user of the separator accordingly may wish to adjustthe pressure differential of the vacuum system or the size of aconstriction in the outlet conduit for the separator, or otherwisesuitably adjust the flow rate through the system to prevent overflow.The users may also temporarily suspend discharge of large quantities ofliquid into the dental chair suction apparatus if the surge tank is onthe verge of becoming full.

It is accordingly preferable that one or more liquid level sensors forsensing liquid level within the surge tank are provided that will causesuitable warning signals to be displayed or heard as the liquid level inthe surge tank increases. For example, the sensing mechanism could sensewhen the surge tank is ¼ full, ½ full, and ⅞ full, and at each thresholdliquid level within the surge tank, could provide a suitable warningsignal (perhaps using lamps of different colors to correspond todifferent threshold levels, etc.). Further, when the liquid level in thesurge tank has reached (say) the ⅞ level, it may be desirable to alertthe users of the system by a more urgent signal (e.g. an audible signal)so that the users will be more urgently warned of the risk that thesurge tank may soon be full.

It is also desirable to monitor solids levels in the sedimentary deposittank or tanks. Solids should preferably accumulate in such tanks only toa fraction of the total tank volume so as not to interfere unacceptablywith the settlement process within baffle chambers. As baffle chambersfill up with solids, liquid flow through the tank become impeded ordeflected and the tank becomes increasingly less effective to promotesettling out of solids. In this specification, reference to a “full”sedimentary deposit tank that should be removed and replaced by a freshtank, or cleaned out, implies a tank filled with solids to the extentthat the user of the system or its designer considers to be acceptable,but does not imply a tank totally filled with solid waste.

Monitoring of solids level within the sedimentary deposit tank may beconveniently be accomplished by a sensor responsive to variations indielectric constant installed at an appropriate location on an exteriorwall of the settlement tank—atop the lid or at the bottom of thesedimentary deposit tank, or preferably at a threshold level positionalong a side wall. Similar such dielectric-constant variablecapacitance-type sensors are commonly used as stud finders for locatingstuds in closed walls. The location of the sensor on an exterior sidewall of the settling tank, so that the sensor path is generallyhorizontal, may be more reliable in that the distinction between liquidand solids in the path of the sensor is more pronounced than the gradualchange in dielectric constant that would be sensed by a sensor atop thetank lid whose sensor path is vertical. In either case, the operatingprinciple is the same—while the solids level in the tank is below thethreshold level established for warning detection by the dielectricsensor, no warning signal is supplied, but when the solids level risesto the threshold level above which the sensor provides a warning signalin response to the change in dielectric constant of the solids in thedetection path of the sensor, a suitable alert signal (audible, visual,or both as required) can then warn the user that the tank is adequatelyfull and should be removed and replaced, or cleaned.

Monitoring of flow activity within the sedimentary deposit tank may beconveniently be accomplished by a sensor responsive to changes indielectric constant between effluent liquid and air installed at the topof the tank. When the dental office is working actively, the sedimentarydeposit tank quickly fills up and liquid rises to at least some extentin the surge tank. When the office shuts down for the day, effluentdrains out of the top of the tank to the extent permitted by the outflowconduit, leaving at least some empty space at the top of the tank. Ifthe dielectric liquid level sensor is installed in that space, thesensor will be responsive to the change in dielectric constant detectedwhen the liquid level in the tank falls below the sensor location. Achemical agent supply pump can be controlled by a suitable controlcircuit which is responsive to the dielectric liquid level sensoraccordingly supply precipitant or other chemical agents at a constantrate determined by the pump to the tank when it is operating, but toshut off when the liquid level in the tank falls below the sensorlocation. This of course may happen during slack times as well asovernight and on weekends, etc.

The particular sensing devices chosen for sensing liquid level withinthe surge tank, the warning signal devices and the electrical means foractuating them can all be of conventional design and are notindividually per se part of the present invention.

While the invention using a vacuum system is operable if its vacuumsource or other source of pressure differential is not connected to thevacuum source for the dental chair suction apparatus, it is convenientand considerably less costly to use a single vacuum pump to serve boththe dental chair suction apparatus and the separator apparatus. While,as mentioned, positive air pressure may be used instead of an airpressure differential maintained by vacuum, the system may be somewhatless complex and less expensive to manufacture if a vacuum system isused throughout, utilizing the vacuum pump already present in the dentaloffice.

In a further embodiment of the invention oriented towards large-scaleinstitutional applications in which many dental chairs or other sourcesof effluent are connected to the same suction and drain services,several parallel-connected sedimentary deposit tanks and associatedapparatus, each such composite apparatus including a surge tank andpreferably one, or alternatively two attached sedimentary deposit tanks,may be operated in parallel to provide sufficient treatment capacity forlarge effluent volumes. In such large installations, fluid flow throughthe individual sedimentary deposit tanks may be controlled by the flowgauge and needle valve means disclosed above, or may preferably becontrolled by one or more separate auxiliary effluent vacuum pumps inorder to reduce the complexity of adjusting multiple needle valves (orsimilar individually adjustable flow control devices for each tank) toequalize effluent flow through multiple deposit tanks.

While the invention has been described in the context of a dental officeand is expected that dentists will be the primary users of theinvention, the invention has application to other similar effluentseparation situations. For example, with suitable changes to meetparticular situations, the invention may be adapted for use withjewellers' effluent, diamond cutting effluent, dental laboratorieseffluent, and the like. Where the effluent contains potentially valuablerecoverable solids, filters and other removal apparatus and proceduresshould be selected to maximize the recovery. Equally, for pollutioncontrol, recovery of environmental contaminants may be desirable.

SUMMARY OF THE DRAWINGS

FIG. 1 is a schematic isometric view of a preferred embodiment ofparticle removal apparatus according to the invention, for particularuse in a dental office.

FIG. 2 is a schematic section view of a vacuum break valve for use inthe apparatus of FIG. 1.

FIG. 3 is a schematic isometric view of the sedimentary deposit tank ofFIG. 1 in exploded view illustrating the internal construction of thesedimentary deposit tank, including baffle chamber walls, removablebaffles and sedimentary deposit tank lid.

FIG. 4 is an isometric view of a multi-surface chevron-shaped baffleunit according to the invention.

FIG. 5 is an isometric view of a multi-surface gable-shaped baffle unitaccording to the invention.

FIG. 6 is a schematic diagram of a dental office vacuum line comprisingdental chair suction apparatus openings, the apparatus according to theinvention, a vacuum pump and drain.

FIG. 7 is a schematic isometric view of a portion of a preferredembodiment of particle removal apparatus according to the invention,showing the surge tank and an exemplary three sedimentary deposit tankscoupled together in series.

FIG. 8 is a schematic isometric view of a portion of a preferredembodiment of particle removal apparatus according to the invention,showing the surge tank and an exemplary three sedimentary deposit tankscoupled together in parallel.

FIG. 9 is a schematic isometric view of an alternative preferredembodiment of a surge tank according to the invention, for use with apositive air pressure system.

FIG. 10 is an isometric view of a preferred embodiment of an outlet pipestructure for a sedimentary deposit tank, illustrating an anti-sludgeprotecting sleeve and needle valve.

FIG. 11 is an isometric view of a preferred embodiment of a large scaleinstitutional application of the present invention, illustrating oneseparate auxiliary effluent pump located downstream of multiplesedimentary deposit tanks.

FIG. 12 is an isometric view of an alternative embodiment of a largescale institutional application of the present invention, illustratingmultiple separate auxiliary effluent pumps located upstream of themultiple sedimentary deposit tanks.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Separator apparatus 10 according to the preferred embodiment of theinvention is shown generally in FIG. 1. The positioning of apparatus 10in combination with the conduits of conventional suction apparatus in arepresentative dental office is illustrated in FIG. 6; for greaterclarity in the latter figure, bypass conduit 26 and pressure balancingvalve (vacuum break valve or air check valve) 22, both of which will befurther described below, are specifically schematically shown. Theseparator apparatus 10 is installed downstream of at least one suctionapparatus opening 9 (sometimes referred to herein as an “operatory”)associated with a dental chair, and upstream of a vacuum pump 11. Thesuction apparatus opening 9, apparatus 10, and vacuum pump 11 areinterconnected to form a vacuum line in which there is a continuousconduit for fluid to flow from each suction apparatus opening 9 to thevacuum pump 11. When operating, the vacuum pump 11 creates a pressuredifferential along the vacuum draw line 77 that is coupled to all vacuumlines upstream, thereby generating a suction force along a path from thevacuum pump 11 through the apparatus 10 and to each suction apparatusopening 9.

Such effluent from the dental chairs and a quantity of air are suckedthrough a suction apparatus exhaust conduit 12, through a surge tankinlet pipestem 13 (FIG. 1), and thence into a surge tank inlet port 14of a surge tank 16. The air inflow required to maintain suction ismaintained either via the dental chair suction outlets 9, or if nodental chair suction line is operating, via vacuum break valve 22 atoppipestem 13, as will be described further below.

The mostly liquid effluent normally passes out of the surge tank 16 viasurge tank effluent outlet basin 18, while an air outlet port 20 passeseffluent air downstream via bypass conduit 26. An optional deflector(not shown) may be positioned at the top of and inside the surge tank16, between the surge tank inlet port 14 and the air outlet port 20, andwould extend downward within surge tank 16 to a selected depth, servingas a baffle to reduce the amount of liquid effluent that is sucked intothe air outlet port 20.

The surge tank effluent outlet port 18 passes effluent out of the surgetank 16 and into sedimentary deposit tank 38 a and thence into furtherdownstream portions of the apparatus 10 for target particle separationand effluent discharge. A manually operated shut-off valve 100 closesthe surge tank outlet basin 18 when the tank 38 a is to be removed forcleaning or replacement. When the vacuum pump 11 is operating, the airpressure differential between the surge tank inlet port 14 anddownstream outlet conduit 77 leading into vacuum pump 11 (see FIG. 6),forces effluent, and some air, out of the surge tank 16 and into thesedimentary deposit tank 38.

A vacuum at the air outlet port 20 is generated when the vacuum pump 11is operating, thereby sucking air out of the surge tank 16, to bedischarged from the apparatus 10 via common outlet conduit 77 into whichbypass line 26 feeds. Matter sucked by the vacuum pump 11, generallyfree of removed solids as will be described further below, is dischargedvia vacuum pump exhaust line 17 into a municipal drain of the publicsewage system 15. Such effluent matter typically includes amalgamparticles and solutes, aluminum oxides used in air abrasion treatment,enamel and dentine from teeth, porcelain, acrylic used in bridges,prosthetic cementing agents such as zinc phosphate cement used in crownsand bridges, and other solid material.

Typically, a pressure differential of the order of 3-10 kPa between theinlet and outlet of the apparatus 10 is sufficient to cause liquideffluent to flow through the system if it is relatively small. However,the pressure differential may have to be higher depending upon thepressure drops within the system, the size of ports, passages, chambers,etc. and the number of dental chairs served. Preferably, an empiricalcalculation is made and the pressure differential is adjusted manuallyto suit the user's requirements, although an automatic feedback systemcould be provided, if desired, to maintain output flow rate within aselected range of values.

Referring to FIGS. 1 and 2, the pipestem 13 terminates at its distal endin a vacuum break valve 22 opening pipestem 13 and thus surge tank 16 tothe ambient air via ports 27 when the valve 22 is open. The valve 22 isbiased closed by a spring 28 or other biasing mechanism and is shownclosed (seated) in FIG. 2. Preferably, the valve 22 is a conventionalair check valve, such as one of the KBI-CV series of check valvesmanufactured by King Brothers Industries (Valencia, Calif.). In normaloperation, a suction force effective at the surge tank air outlet port20 draws air into the air bypass line 26, while the suction forceeffective at outlet basin 18 draws effluent liquid into the surge tank16 from line 12. When the dental office suction apparatus openings 9(FIG. 6) are closed and consequently suction apparatus line 12 isclosed, the pressure inside the surge tank 16 drops as a result of thevacuum caused by the vacuum pump 11, and the increased pressure dropovercomes the biasing force of the spring 28, causing the vacuum breakvalve 22 to open, permitting replacement air to enter the surge tank 16and both the airflow and liquid effluent flow to be maintained throughthe system. When the suction apparatus openings 9 are reopened, airentering into the surge tank 16 through the surge tank inlet port 14neutralizes the pressure differential at the vacuum break valve 22,permitting the spring 28 to re-close the vacuum break valve 22. Thepressure drop at which valve 22 opens can be adjusted by varying theselected compression and stiffness of the spring 28.

The level sensor port 24 shown atop surge tank 16 in FIG. 1 receives alevel sensor probe 30 inserted therethrough and sealed into the sensorport 24, only the upper portion of which probe 30 appears in FIG. 1.Preferably, the probe 30 is a conventional fluid level detection sensorresponsive to changes in dielectric constant between effluent fluid andair and having a plurality of sensing means, each sensing meansconnected to an associated wire pair among the wire pairs of a levelsignal cable 25, the sensing means being vertically spaced from oneanother within the surge tank 16. When the liquid level within surgetank 16 reaches any particular sensing means, the sensor is responsiveto the change in dielectric constant between the air and the effluentfluid in the surge tank 16, and transmits a signal along the wire pairattached to the sensor. The associated wire pairs of cable 25 connectthe liquid level sensors to warning display unit 32. The display unit 32comprises one or more audible alert devices 34 and a series of visualalert devices 35 that are responsive to the data level signals so as toprovide alert or warning signals indicating the level of effluent withinthe surge tank 16. In a preferred embodiment, the probe 30 responds toliquid levels within the surge tank 16 at the ¼ full, ½ full, ¾ full and⅞ full values, and at each such liquid level, the display unit 32provides a suitable warning signal using, for example, lamps ofdifferent colors to correspond to different liquid levels. Further, whenthe liquid level in the surge tank 16 has reached the ⅞ level, the useris alerted by a more urgent signal (e.g. an audible signal) warning ofthe risk that the surge tank 16 may soon be full. The user may inresponse to such warning increase the flow rate out of sedimentarydeposit tank 38, or reduce the incidence of use of the dental chairsuction drains 9, or take other remedial measures. In an alternativeembodiment, the liquid level sensor means may be mounted externally onthe sides of the surge tank 16 located at appropriate levels to indicatewhen the tank is ¼ full, ½ full, ¾ full and ⅞ full, for example.

If effluent is deposited into the surge tank 16 when the surge tank 16is full, excess effluent is sucked through the air outlet port 20 and ispulled by vacuum pump 11 along liquid bypass conduit 120 running inparallel with the air bypass conduit 26 and discharged from theapparatus 10 into the municipal drain (thereby preventing effluent frombacking up through the pipestem 13, suction apparatus exhaust conduit12, and eventually the suction apparatus openings 9). Preferably, noeffluent is deposited into the suction apparatus openings 9 when thesurge tank 16 is full, as target particles in the effluent dischargedthrough the air bypass conduit 26 will not be separated from theeffluent by sedimentary deposit tank 38. As a precaution in the eventthat passage of liquid effluent containing solid particles through thebypass conduit 26 does occur, pinnacle filter 89 (FIG. 1) is intended tocatch at least the larger target particles that are present in sucheffluent, thereby tending to avoid damage to the vacuum pump 11 and toafford an “insurance” opportunity to remove unwanted particles beforethey pass into the municipal system. However, it is best to avoidoperation of the system that results in any passage of liquid throughbypass conduit 26.

Referring to FIGS. 1 and 3, effluent from surge tank outlet basin 18passes through a sedimentary deposit tank inlet port/pipestem/coupling36 a and into sedimentary deposit tank 38 a. The sedimentary deposittank 38 a is provided with a plurality of baffle chambers 42, 44, 46,48, 50, 52, one or more precipitant inlet ports 53 sealed to the top ofsedimentary deposit tank 38, and a deposit tank outlet conduit/pipestem55 a.

As shown in FIG. 3, the baffle chambers 42, 44, 46, 48, 50, 52 arebounded by transverse baffle chamber boundary walls 54. Each bafflechamber wall 54 is arranged vertically and parallel to the other bafflechamber walls 54. Each baffle chamber wall 54 has a wall opening 56 inthe form of a rectangular notch located near the top edge of the bafflewall 54. The wall openings 56 alternate in transverse position so as tomaximize the effluent travel distance from one wall opening 56 to thenext. The side and bottom edges of each baffle chamber wall 54 areconnected to the interior surfaces of the sedimentary deposit tank 38 ato form a fluid-tight seal so that effluent can flow from one bafflechamber to an adjacent baffle chamber only through the common bafflechamber wall opening 56. In a preferred embodiment of the sedimentarydeposit tank 38 a the baffle chamber walls 54 are formed as integralparts of the tank unit. Alternatively, in a further embodiment of thesedimentary deposit tank 38 a, the baffle chamber walls 54 may be formedseparately from the tank 38 a and may be removably inserted into matingslots located on the walls and bottom of the deposit tank 38 a to dividethe tank into separate baffle chambers.

In the preferred embodiment, the baffle chambers comprise, in downstreamorder: an inlet baffle chamber 42, a second baffle chamber 44, a thirdbaffle chamber 46, a fourth baffle chamber 48, a fifth baffle chamber50, and an outlet baffle chamber 52, although the number and size ofbaffle chambers is within the designer's discretion.

Referring to FIGS. 3, 4, and 5, the inlet, second, third, fourth andfifth baffle chambers 42, 44, 46, 48, 50 comprise inclined (either inone dimension or two dimensions) baffle units 67, 68 selectivelyarranged within each baffle chamber 42, 44, 46, 48, 50, 52 so that eachbaffle unit 67, 68 directs the fluid flow but does not interrupt it. Ina preferred embodiment of the invention, the baffle units 67, 68 may beeither chevron-shaped elements 67 as shown in FIG. 4 or gable shapedelements 68 as shown in FIG. 5, depending on the needs of the user andthe characteristics of the effluent to be treated. In an alternativeembodiment, the baffle surfaces may be simply inclined planar surfaces,similar to those disclosed in the applicant's previously published POTInternational Patent Application No. PCT/CA99/00665 filed on Jul. 21,1999, from which this application claims priority. Referring to FIG. 3,liquid passes from inlet baffle chamber 42 to the second baffle chamber44 via port 56, from the second baffle chamber 44 via a second port 56to the third baffle chamber 46, and thence to the fourth baffle chamber48 via a third port 56. Preferably, the surfaces of the baffle units 67,68 lie at an angle of about 60° to the deposit tank floor 69, and in thecase of the gable-shaped baffle units 68 angled in two dimensions, asecondary angle of about 30° to the baffle chamber walls (54) so as tooptimize convection of the effluent through the baffle chambers andparticle separation. The user may wish to consult published experimentalstudies of preferred inclined sedimentation techniques, such asImportance of Convection to the Enhancement of Erythrocyte SedimentationRates in Inclined Tubes, Hocking et al. (Biorheology, 24; 473-482,1987). Hocking shows that the rate of settling of erythrocyte particlesfrom liquid whole blood onto a surface increases as the angle of thesurface is increased, reaching a maximum settling rate when the surfaceis 60° from the horizontal plane, and that selective placement of thesurfaces encourages advantageous fluid flow patterns for increasedparticle separation.

In a preferred embodiment of the invention designed to minimizemanufacturing costs associated with producing baffles, chevron orgable-shaped baffles 130, 135 are formed individually with attachedflanges or ribs 132, 136 to provide for separation of multiple baffleswhen stacked in a baffle chamber. In the case of chevron-shaped baffles130, such separation ribs 132 are located near the outer edges of thebaffle, and may be oriented parallel to effluent flow as illustrated inFIG. 4, or alternatively, perpendicular to effluent flow, similar toribs 135 shown in FIG. 5. Such separation ribs 132 may also be locatedalong the baffle centerline, and may be rectangular or cylindrical incross section. In the case of gable-shaped baffles 135, such separationribs 136 are located near the outside edges of the baffle, and near thecentral apex of the baffle, and may be oriented parallel orperpendicular to effluent flow similar to ribs 132 and 136 in FIGS. 4and 5, or may alternately be located along the baffle centerline, andmay be rectangular or cylindrical in cross section. In a furtherpreferred embodiment designed to minimize the cost of assemblingsedimentary deposit tank equipment, two or more baffles 130, 135 may beformed together as a single integrated baffle unit 67, 68 includingspacing ribs 132, 136 to align and separate the baffles as discussedabove. In such an embodiment, for applications where gable-shapedbaffles 135 are used, three gable baffles 135 are preferably formedtogether in a vertically stacked configuration to form a singlegable-shaped baffle unit 68. In applications where chevron-shapedbaffles 130 are used, it is preferable to form two chevron baffles 130together in a vertically stacked configuration to form a singlechevron-shaped baffle unit 67. It is desirable to utilize variations inthe number and separation (i.e. relative spacing) of baffles used in abaffle chamber (either as individually formed and stacked baffles or asjointly formed baffle units) in order to customize the arrangement ofbaffles inside the sedimentary deposit tank 38 a, depending on thecharacteristics of the effluent to be treated. For example, in anapplication where the effluent to be treated is expected to contain asignificant portion of very small particles, in addition to largerparticles, it may be advantageous to utilize a greater number of baffleswith smaller spacing therebetween in the downstream baffle chambers ofthe sedimentary deposit tank 38 a, in order to increase thesedimentation of smaller particles after the larger particles havesettled out in the upstream baffle chambers. It is expected that suchvariations in baffle configuration are best determined empirically, asthey are dependent on factors such as effluent characteristics, whichmay vary significantly between applications.

Baffle chamber 42 is configured slightly differently from the otherbaffle chambers in order to accommodate the inlet pipestem 36 a. Bafflechambers 44, 46 and 48 may be essentially identical, but the interiorarrangement of the chambers and the respective size of the chambers isat the discretion of the designer.

Effluent passing into the sedimentary deposit tank 38 a through thedeposit tank inlet port 36 a first collects in the inlet baffle chamber42. As time elapses, metal particles and other solid particles heavierthan the liquid effluent separate from the effluent and settle on thesurface of a baffle unit 67 or 68 or on the sedimentary deposit tankfloor 69; the more time that elapses, the greater the amount ofgravity-induced particle separation. To separate solute metal particlesdissolved in the liquid effluent, a chemical agent such as aprecipitant, chelating agent, or flocculent may be controllablydelivered via one or more inlet port(s) 53 by one or more deliverypump(s) 23 fed by one or more supply vessel(s) 70 and injecting chemicalagent via supply conduit 29 sealed into port 53. Preferred chemicalagents for dental office use include precipitants potassium iodide (KI)or sodium borohydrate (NaBH₄) mixed with sodium hydroxide (NaOH) orsodium sulfide (Na₂S), the latter combination however having a sulfurousodour, and the chelating agent EDTA, however any precipitant orchelating agent suitable for combining with solute mercury or silver orboth, may be selected. Supplied in 1-molar concentrations, thesechemical agents may be added to the effluent in the ratio of about 2parts per 1000. Strong oxidizing or reducing agents should not be usedin significant concentrations, as they may release mercury fromparticulate amalgams. Addition of a flocculant to a precipitant orchelating agent may promote further particle separation from theeffluent; fungicides and antibacterial agents may also be contained inthe supply vessel 70. The flocculant, if present, combines with metalparticles and causes such particles to combine into larger masses, sothat metal particle separation is further promoted. Suitable flocculantsinclude aluminium sulfate and aluminium chloride. Anti-fungal agentsinclude acridine dyes and anadine dyes.

The pump 23 may operate at a constant speed, delivering a constant flowof chemical agent into the tank 38 a while operating. However, the pump23 should not operate when the dental office is idle during slack times,overnight or during weekends, etc. To this end, the pump 23 operatesunder the control of a liquid level sensing probe 117 located at the topof tank 38 a, or preferably, attached to the side of the tank 38 a, nearthe top thereof. The probe 117 may comprise a sensor responsive tochanges in dielectric constant of the same general sort as describedpreviously with reference to level sensing probe 30. During idle hours,liquid in the surge tank 16 will drain into the tank 38, and eventuallythe level in the tank 38 a will fall to a rest level determined by theheight of the orifices 56. The sensing means of probe 117 should bepositioned so that the sensing means detects the change in dielectricconstant between the effluent and air and transmits a signal to asuitable control circuit just before the liquid level in tank 38 areaches rest level. The pump 23 is controlled by the control circuit tooperate when the sensing means reports the dielectric constant of theeffluent, indicating that the liquid level in tank 38 a is above therest level and the system is in operation.

Alternatively, the chemical agent delivery apparatus 70 could respond toa time clock to deliver a selected amount of chemical agent per selectedtime interval (with a selection of zero for idle hours). In a morecomplex arrangement, the delivery apparatus 70 could respond in part tothe flow rate of effluent passing out of tank 38 a as determined by thesetting of needle valve 85. The amount of chemical agent selected to beapplied per time interval or per unit of effluent flow will be dependentin part on the chemical characteristics of the agent selected, and inpart upon the expected concentration of particles in the effluent, andis usually best determined empirically.

Located at the fifth baffle chamber 50 and outlet baffle chamber 52 aremodular filtration or adsorption inserts 65, 66 which may be adapted toinclude a range of physical and chemical characteristics, depending onthe needs of the system user and the characteristics of the effluent tobe treated. Such modular inserts are constructed to allow easy removaland replacement within the sedimentary deposit tank 38 a followingsaturation of filter or absorbent material with particulate or otherwaste matter. In a preferred embodiment, one of the modular units 65, 66may be adapted to include an outlet baffle chamber filter positioned sothat effluent passing through the outlet baffle chamber 52 and throughthe deposit tank outlet pipestem/port/coupling 55 a must first passthrough the baffle chamber filter. The filter can be of fine mesh orfibrous mat or the like within a constraining cage. Preferably, thefilter is made from polystyrene or polyethylene or another biologicallyinactive material so that microbes cannot utilize the filter materialfor nutrients. The filter tends to catch any floating solid matter aswell as any coarser solid matter that has not settled out in theupstream baffle chambers. Preferably, any precipitants, flocculants orother chemical agents used should not generate an abundance of floatingsolid matter, because otherwise the filter could be quickly clogged. Ifnecessary, the size of the filter and of the final two baffle chambers50, 52 can be increased if a high proportion of floating matter isexpected to be entrapped.

In a further preferred embodiment, one of the modular units 65, 66 maybe adapted to include absorbent material used to adsorb dissolvedmercury or other metal ions from effluent solution. A preferredadsorbent material is finely divided bentonite clay particles, combinedwith activated silica particles to form granular pellets, which may beenclosed in a porous and permeable membrane, similar in function andappearance to a tea bag. Concentrated chlorine solution may also beadded to the effluent directly upstream of such an adsorbent modularunit through an appropriately located injector port 53. Suchconcentrated chlorine solution is effective to release metal ions fromdissolved organic compounds to facilitate more efficient adsorption bythe bentonite clay particles in the adsorbent modular unit, while theactivated silica particles in the modular unit are effective to adsorbsuch dissolved organic compounds. In another preferred embodiment, oneof the modular units 65, 66 may be adapted to include an auxiliary fineparticulate filter, which is effective to remove residual fineparticulate matter that has not settled out of suspension in theupstream baffle chambers 42, 44, 46, 48 of the sedimentary deposit tank38 a. A possible construction of the auxiliary filter is detailed belowin the description of an alternative external embodiment of the filter.

In the alternative embodiment of the auxiliary fine particulate filtershown in FIG. 1, effluent passing out of tank outlet pipestem 55 a nextpasses into the auxiliary filtration unit 74 located external to anddownstream of the sedimentary deposit tank 38 a for a final separationof fine particles. Preferably, the filter is an inorganic polymer filterfor separating aqueous mercury from liquid. An example of such filter isdisclosed in Pierce et al. Chemically designed inorganically polymerfilters for aqueous mercury separation, (Journal of Dental Researchv.44, p.404, 1997) Alternatively, the filter of filtration unit 74 canbe a conventional dual gradient cartridge filter. Additionally meshfilters or porous membranes may also be employed depending uponavailable pressure differentials, flow-rate targets, and size ofparticulate desired to be removed. The outlet of filtration unit 74 isconnected via outlet conduit 82 and thence via needle valve 85 to thecommon exit conduit 77. The filtration unit 74 is preferably attached tothe deposit tank 38 a using quick release connectors to enable easyreplacement of the modular filtration unit 74 as required.

In a preferred embodiment of the invention that includes a fineparticulate filter 74 in a modular unit 66 of the sedimentary deposittank 38 a, the outlet pipestem 55 a of the tank includes protectivesleeve assembly 144 to prevent clogging of the needle flow rate controlvalve 85 caused by floating particulate matter and froth or sludge whichcan accumulate around the exit port 55 of the tank. Such protectivesleeve assembly comprises a downwardly depending inner needle valveintake pipe 142 over which is fitted a downwardly depending protectivesleeve 144, which extends below the lower extremity of the inner intakepipe 142 by a margin of comfort to protect against the entrance offloating particulate matter or sludge into the intake pipe 142. Theprotective sleeve 144 is perforated by several radially spaced air holes146 located near the top of the sedimentary deposit tank 38 a such thateffluent is drawn into the intake pipe 142 only when the fluid level inthe tank is higher than the level of the lower end of the intake pipe142. If the fluid level in the tank 38 a drops below the level of thelower end of the intake pipe, air entering the air holes 146 in theprotective sleeve 144 will be drawn out of the tank through the needlevalve intake pipe 142 in place of effluent.

A disinfectant is added to the effluent at the individual operatorysuction openings 9 to control bacterial growth and odours in theeffluent treatment system. The addition of disinfectant additionallyserves to break down organic particles in the effluent, releasingcomplexed forms of mercury and other metals, which can then be removedfrom solution in the settlement tank 38 through the use of chemicalagents or adsorbent compounds. Preferred disinfectants are chlorine,bromine, or peroxide based, and utilized in a solid dissolvable brickform which is held in place at the individual suction openings 9 by aholding screen located in or near the opening 9 in the vacuum line.

It should be noted that depending on the choice of chemical agents(precipitant, flocculent, chelating agent, disinfectant and adsorbent)selected for use in the treatment system, there exists a possibility fordisadvantageous chemical interactions to occur, reducing theeffectiveness of one or more of the agents in use. Such chemicalinteractions may also be affected by the composition of the effluentbeing treated in the system. Therefore, an optimum combination ofchemical agents for use in treatment of a specific effluent stream maybe determined by empirical means.

Note that the flow rate of effluent through tank 38 a must be low enoughthat target particles have adequate opportunity to settle out. In atypical dental office using a vacuum pump 11, drawing a vacuum of about25-50 kPa, a vacuum differential pressure between inlet port 14 andoutlet conduit 82 of about 3-10 kPa should be sufficient to establish asuitable flow rate through tank 38 a, assuming a maximum effluent volumeof about 5 to 10 liters between inlet port 14 and outlet conduit 82.Flow rate may be adjusted by means of a needle valve 85 in tank outletline 76 coupled downstream of the outlet pipestem 55 a atop the tank 38a and connected to the final baffle chamber 52; a flowmeter 87 permitsthe operator to read the current flow rate and to adjust it as requiredusing the needle valve 85. The flow rate should be set to an empiricallyestimated optimal rate equal to the total expected effluent volumeduring a duty cycle divided by the total available time for operatingthe sedimentation system per duty cycle, and multiplied by anappropriate safety factor (greater than 1.0) to guard against systembackup or overflow. For example, if an average dental chair producesabout 1 liter of effluent per duty cycle (working day), and there are 8dental chairs in the office served by the apparatus 10 which operatesover the 8 hour working day, a needle valve flow rate setting of about1.2 L/hr (20 mL/min) would accommodate all 8 chairs and provide a fairlysteady rate of flow through the sedimentary deposit tank 38 throughoutthe duty cycle, incorporating a safety factor of 1.2 to guard againstsystem backup. These devices 85, 87 are preferably positioned in theseparation system downstream of any removable modular devices such asthe tank 38 a and any auxiliary filter 74 present, and upstream of thejunction of the tank exit conduit 79 leading from tank 38 a and thecommon exit conduit 77.

It is desirable to utilize the minimum possible flow rate of effluentthrough the separation system to maximize the time for the particles toseparate from the effluent. However, the flow rate may be changed if,for example, the surge tank 16 becomes backed up with effluent. Thevolume of effluent per dental chair per day may vary office by officeand pursuant to national preferences, regulations, etc. The use ofcuspidors, ultrasonic scalers and other optional dental office equipmentmay increase the volume of effluent produced. The optimal effluent flowrate through the sedimentary deposit tank 38 a can be estimatedempirically as outlined above such that the total effluent volumegenerated during a duty cycle passes through the system as slowly aspossible without overflowing the surge tank 16. The flow rate throughthe apparatus 10 may be further controlled (in addition to by adjustingthe needle valve 85) by adjusting the suction force of the vacuum pump11.

There is a tendency of particles to settle out in the upstream bafflechambers rather than the downstream baffle chambers within tank 38. Sothe upstream chambers tend to fill up and clog the undersides of thebaffles 67, 68 before the downstream chambers become very full of solidmatter. A balance must be struck between maintaining optimal operationof the baffles, on the one hand, and avoiding undue frequency ofcleaning or replacement of tanks 38, on the other hand. The user shouldchoose empirically how full a tank 38 a must be before it is cleaned outor replaced by a fresh empty tank. To this end, a solids level sensor116 may be provided to indicate the level of deposited solids in, say,the third or fourth baffle chamber of the tank. Dielectric constantsensor technology similar to that commonly used in “stud sensor” unitsmay be used for such a solids level sensor, where the sensor 116 isresponsive to the change in dielectric constant between effluent liquidin tank 38 a and deposited solids. When the level of solids rises to thelevel of the sensor, the sensor detects the change in dielectricconstant, transmitting a signal to an appropriate control circuitlocated in display box 32 via signal cable 45. When that happens, thecontrol circuit in display box 32 provides a warning (by warning lamp orthe like) that the tank 38 a is full and should be cleaned out orreplaced by a fresh empty tank. While FIG. 1 shows an alternativeembodiment of the invention wherein the solids level sensor 116 ismounted to the top of the sedimentary deposit tank and protrudestherein, in a preferred embodiment of the invention, such sensor 116 maybe mounted on the outside of the side wall of the third or fourth bafflechamber of the tank at a threshold level selected by the user.

Periodically, it is desirable to remove the metal particles collected inthe sedimentary deposit tank 38 a and filtration unit 74. According tothe preferred embodiment, the sedimentary deposit tank 38 a andassociated integrally constructed auxiliary modular filtration units 65,66 are removably connected to the apparatus 10 as readilycoupled/decoupled modular units. To this end, all conduit or portcouplings and all electrical connections should be of the quick-releasetype. The tank 38 a and other modular units can be removed from theapparatus 10 for metal particle recovery and cleaning, for example, at ametal particle recovery facility.

The air bypass vacuum line 26 is coupled to the surge tank 16 via abypass coupling collar 88 that is adapted to removably connect thevacuum line to the air outlet port 20, and the base of pipestem 13 alsopreferably includes a release coupling so that the surge tank 16 may bedecoupled for cleaning.

Bypass conduit 84 including shut-off valve 86 connects the surge tankpipestem 13 to the air bypass line 26. The bypass valve 86 is normallyclosed when the surge tank 16 and sedimentary deposit tank 38 a areconnected to the apparatus 10, but is opened when the tank 38 a isremoved. When the sedimentary deposit tank 38 a is removed, valve 100leading from exit basin 18 is closed. Eventually the surge tank 16 maybecome full of effluent. Air then passes through the suction apparatusexhaust conduit 12, through the upper portion of pipestem 13, throughthe by-pass conduit 84, and into the air bypass conduit 26, fordischarge into the vacuum draw line 77 and thence into the municipaldrain. When eventually liquid effluent passes from a full surge tank 16out of outlet port 20, the liquid passes through liquid bypass conduit120 running in parallel with the air bypass conduit 26, and eventuallyjoins common exit conduit 77 upstream of pinnacle filter 89. Thistemporary vacuum circuit enables the dental office suction apparatus tokeep functioning, albeit without as much solids removal as would occurif tank 38 a were connected, but with some solids removal by means ofpinnacle filter 89.

To avoid temporary problems associated with removal and replacement orcleaning of sedimentary deposit tank 38, it is desirable to use two ormore modular sedimentary deposit tanks operating in parallel or series.FIG. 7 illustrates an exemplary series connection of three sedimentarydeposit tanks 38 a, 38 c, 38 d, and FIG. 8 illustrates an exemplaryparallel connection of three sedimentary deposit tanks 38 a, 38 e, 38 f.Each such sedimentary deposit tank would be provided with its own solidslevel indicator so that each upon being considered “full” would beremoved and replaced. The use of two or more sedimentary deposit tanksin series extends the flow distance for the effluent to pass through theapparatus 10 compared to that for a single sedimentary deposit tank.Therefore, greater separation of particles may be achieved for a givenflow rate, or a higher flow rate may be applied through the apparatus10.

If a positive air pressure source instead of a vacuum source isconnected to provide the requisite pressure differential between theinlet port of the surge tank 16 and the exit conduit 77, or if thevacuum pump 11 may be operating only intermittently, a modified versionof the plumbing atop the surge tank 16 as shown in FIG. 9 isappropriate. (In Europe, it is common for the vacuum pump 11 to turn offwhen not in active use; in North America, the vacuum pump 11 tends torun constantly, at least during office hours.) Valves 118 and 119,interposed between the surge tank 16 and conduits 12 and 26respectively, are normally open when the dental office drains areoperating, in which case the positive upstream air pressure in line 12drives effluent downstream through the surge tank 16 and sedimentarydeposit tank 38, and drives air downstream through air bypass conduit26. When the dental office drains are not operating, in which case noupstream air pressure is applied, both valves 118, 119 close In suchlatter instance, an air inlet port 112 located in the upper part of thesurge tank 16 opens, applying a modest air pressure to the interior ofthe surge tank 16 to compensate for the lack of air pressure in conduit12. Valve 118 can be a check valve that, like valve 22, operates inresponse to pressure changes. Valve 119 and the air pressure supply toair inlet port 112 may be solenoid actuated in response to interruptionin the supply of air pressure to conduit 12. The supply of air to airinlet port 112 is also preferably responsive to liquid level sensorprobe 117 or the equivalent, so that positive air pressure is no longerapplied once the liquid level in tank 38 a has dropped below thethreshold level determined by the probe 117 or the like.

In some working environments, the apparatus described above whoseprimary use is for solids removal may be provided with auxiliaryconduits for removing excess effluent from a full sedimentary deposittank that has been replaced, and drying the tank. Such full tankcontains mostly liquid and some solid. Assuming that the full tank is tobe taken off premises for solids removal and waste recovery andcleaning, the tank is more easily handled if it is not full of liquidbut is relatively dry. To this end, an attachment conduit 125 fittedwith a valve 126 is connected to the inlet port of the surge tank 16 andis also connected to the outlet port 55 b of the full sedimentarydeposit tank to be dried. By tilting the full tank, and opening thevalve on the attachment conduit, the excess liquid effluent can beremoved from the full tank under suction, returning the effluent to thesurge tank 16 and flow therefrom for retreatment in the newly installedempty sedimentary deposit tank. Following removal of excess liquideffluent from the full tank, auxiliary tank drying conduits 92, 93 mayeach be coupled at one end to bypass conduit 26 and at the other endrespectively coupled to pipestem couplings 36 b, 55 b respectively of atank 38 b to be dried, as illustrated in FIG. 1. A shut-off valve 114 isinterposed in line 26 between the points of connection of conduits 92,93 with the line 26. Shut-off valves 115, 113 respectively are providedfor the conduits 92, 93. When tank 38 b is to be dried, valves 115, 113are open and valve 114 is closed, forcing the air entering line 26 topass through conduits 92, 93 and therefore the interior of tank 38 b,thereby permitting the flowing air to remove water vapour from the tank38 b. When the dried tank 38 b is to be removed and another tank put inits place, or whenever the drying option is not to be used, valves 115,113 are closed and valve 114 is open, directing the air along conduit 26without passing through conduits 92, 93.

As the air entering the conduit 26 is invariably humid, the dryingoption described above may not work well in all situations. A heater(not shown) could be provided to warm the air before it enters tank 38b, but that increases the expense of manufacture and the operatingexpense. An auxiliary tank drying apparatus separate from the effluenttreatment apparatus would be more economical in some situations.

Mercury vapour may remain in the air line; it will not be entrapped bythe sedimentary deposit tank 38 a nor by filters downstream thereofbecause the vapour preferentially passes through bypass conduit 26. Amercury vapour trap or filter 101 may be provided in the conduit 26 toremove at least some mercury from the effluent air. A suitable mercuryvapour filter is described in Boliden U.S. Pat. No. 5,205,743 issuedApr. 27, 1993; selenium is a suitable material for use in such filters.Activated charcoal impregnated with various active mercury bondingagents may also be used. Note that the mercury vapour trap will alsocatch such vapour emanating from the tank 38 b being dried.

Note that the provision of liquid effluent bypass conduit 120 locatedbeneath air bypass conduit 26 permits excess liquid to flow from surgetank 16 to common exit conduit 77 without interfering with air flowthrough the drying conduits 92, 93 and without interfering with theoperation of the mercury vapour filter 101. The bypass line 120 shouldjoin conduit 77 upstream of pinnacle filter 89 so as to remove at leastcoarser solids in the event of such overflow from surge tank 16.

An alterative embodiment of the present invention is oriented towardsinstitutional or other large-scale use where many dental chairs or othersources of effluent are connected to the same suction and effluentdischarge services, such that the volume of effluent generated during aduty cycle exceeds the capacity of a single settlement tank 38. In onesuch large scale installation, the effluent travels through two or moresettlement systems arranged in parallel, each settlement system composedof a surge tank 16 connected to preferably one, but alternatively twosettlement tanks 38. The common main vacuum line 12 connects to two ormore surge tanks 16 a, 16 b through one or more T-junction connectors.Similarly, the treated effluent exiting the settlement tanks 38 throughthe tank exit conduits 79 are connected to a common main exit conduit77. The pressure differential required to move the effluent through theparallel settlement systems can be provided by the common system vacuumpump 11 as in the small dental office installation described above, orby a separate auxiliary effluent pump 160.

The use of a separate effluent pump 160 allows the settlement system tooperate 24 hours per day, independent of the operation of the systemvacuum pump 11. This allows the reduction of the minimum possibleeffluent flow rate by lengthening the settlement time to processeffluent from one duty cycle, optimizing sedimentation. Therefore, theoptimum effluent flow rate becomes the total volume of effluentgenerated in one duty cycle (an 8 hour working day) divided by the totalavailable time for operation of the system per duty cycle (24 hours dueto continuous operation of effluent pump 160), multiplied by anappropriate safety factor to guard against system backup. Additionally,a separate effluent pump 160 also eliminates the need to individuallycalibrate vacuum needle valves 85 on each settlement tank 38 in order toensure equal effluent flow through each tank 38 installed in parallel.Instead, in an installation where a separate effluent pump 160 isutilized, the main system vacuum pump 11 is connected only to the surgetanks 16, but not also to the individual settlement tanks 38 as in thesmall dental office installation. In addition, when a separate effluentpump 160 is used, the treated effluent leaving the settlement tanksthrough tank exit conduits 79 flow into a common effluent drain 162which is separate from the main vacuum exit conduit 77.

As shown in the preferred embodiment of a large institutionalinstallation in FIG. 11, the separate effluent pump 160 is preferablylocated downstream of the settlement tanks 38 g, 38 h in order to reducewear on the pump caused by abrasion from amalgam and other particlessuspended in the effluent before sedimentation, and to reduce thedissolution of mercury into the effluent caused by the turbulence insidethe effluent pump 160. In an alternative embodiment shown in FIG. 12,multiple separate effluent pumps 160 a, 160 b can be located upstream ofthe settlement tanks 38 g, 38 h between the individual surge tanks 16 a,16 b and the settlement tanks 38 g, 38 h to force effluent through thetanks by positive pressure. The schematic representations of the largeinstitutional installations shown in FIGS. 11 and 12 omit many of thedetailed elements of the treatment system for the sake of clarity,however, it is expected that the additional system elements as shown inFIGS. 1, 2 and 9 and described in the foregoing will remain part of suchinstitutional installations including such elements as fluid and solidlevel sensors and control systems, conduits and flow control valves,chemical agent injection ports and supply pumps, pinnacle filters,auxiliary effluent suction conduits, and the like.

Other alternatives and variants of the above described methods andapparatus suitable for practising the methods will occur to thoseskilled in the technology. The scope of the invention is as defined inthe following claims.

What is claimed is:
 1. Apparatus for separating particles from liquideffluent containing such particles, the liquid effluent flowing from aneffluent source to an effluent destination such as a sewer or drain, theapparatus comprising: (a) a surge tank for receiving the liquideffluent, the surge tank having a surge tank inlet for connecting to theeffluent source and a surge tank effluent outlet; (b) a sedimentarydeposit tank having a sedimentary deposit tank inlet connected to thesurge tank effluent outlet for receiving effluent from the surge tank,and a sedimentary deposit tank outlet for connecting to the effluentdestination, and within which sedimentary deposit tank the particlessettle out from the liquid effluent, the portion of the particles thatsettle out being inversely related to the flow rate of the liquideffluent through the sedimentary deposit tank, in that the higher theflow rate the smaller the portion of the particles that settle out; (c)means for receiving and applying a pressure differential between thesurge tank and the sedimentary deposit tank outlet so as to cause thesurge tank interior to be at a higher pressure than the sedimentarydeposit tank outlet; (d) means for inhibiting the flow of liquideffluent in its passage from the inlet of the surge tank through to theeffluent destination thereby to control the flow rate of effluentthrough the sedimentary deposit tank; (e) an air bypass conduit forestablishing a fluid interconnection between the vicinity of the surgetank inlet and the vicinity of the passage of the effluent downstream ofthe sedimentary deposit tank outlet; wherein when the surge tankcontains liquid effluent and the pressure differential is appliedbetween the surge tank and the sedimentary deposit tank outlet, thepressure differential and flow inhibiting means cause the liquideffluent to flow at a slow flow rate through the sedimentary deposittank, the slow flow rate facilitating settling of the particles withinthe sedimentary deposit tank.
 2. The apparatus of claim 1, wherein themeans for receiving and applying a pressure differential comprises meansfor connecting the sedimentary deposit tank outlet to a pump suitablefor drawing liquid effluent from the sedimentary deposit tank.
 3. Theapparatus of claim 1, wherein the means for receiving and applying apressure differential comprises means for connecting the apparatusin-line to a vacuum system, the vacuum system having a suctioning devicefor suctioning liquid effluent and having a vacuum pump suitable forpassing both gas and liquid, wherein: (a) the surge tank inlet issuitable for connecting to the suctioning device; (b) the surge tank hasa surge tank air outlet suitable for connecting to the vacuum pump; (c)the surge tank is configured so as to permit air entering the surge tankthrough the surge tank inlet to pass out of the surge tank through thesurge tank air outlet; and (d) the sedimentary deposit tank outlet issuitable for connecting to the vacuum pump; wherein, when: the surgetank inlet is connected to the suctioning device; the surge tank airoutlet and the sedimentary deposit tank outlet are connected to thevacuum pump; the suctioning device is open so as to permit liquideffluent and air to enter the vacuum system; and the vacuum pump isoperating, so as to cause the pressure at the suctioning device to behigher than the pressure inside the surge tank and the pressure insidethe surge tank to be higher than the pressure at the sedimentary deposittank outlet, (e) the pressure differential between the suctioning deviceand the surge tank causes air and liquid effluent drawn into thesuctioning device to flow into the surge tank through the surge tankinlet; and (f) the pressure differential between the surge tank and thevacuum pump causes, (i) air to flow through the surge tank air outlet tothe vacuum pump, and (ii) liquid effluent to flow through thesedimentary deposit tank and out the sedimentary deposit tank outlet. 4.The apparatus of claim 3, further comprising a pressure balancing valvelocated upstream of the surge tank effluent outlet for maintaining thepressure differential between the surge tank and the sedimentary deposittank outlet, the pressure balancing valve including means, responsive tothe pressure in the vicinity of the surge tank inlet, for opening andclosing the pressure balancing valve, wherein: (a) the pressurebalancing valve opens to permit air to flow into the surge tank inresponse to a pressure in the vicinity of the surge tank inlet lowerthan required to maintain the pressure differential between the surgetank and the sedimentary deposit tank outlet; and (b) the pressurebalancing valve closes to prevent air from flowing into the surge tankthrough the pressure balance valve in response to a pressure in thevicinity of the surge tank inlet at least roughly equal to that requiredto maintain the pressure differential between the surge tank and thesedimentary deposit tank outlet.
 5. The apparatus of claim 4, whereinthe pressure balancing valve is located in the vicinity of the surgetank inlet.
 6. The apparatus of claim 1, wherein the means for receivingand applying a pressure differential comprises means for connecting theinterior of the surge tank to a source of air under pressure whereinwhen the surge tank is connected to the source of air under pressure,the pressure in the surge tank is higher than the pressure at thesedimentary deposit tank outlet.
 7. The apparatus of claim 6, furthercomprising a valve for opening and dosing the connection between thesurge tank inlet and the effluent source so that: (a) the valve can beclosed, so as to prevent the air under pressure from causing effluent toflow back to the effluent source, when the interior of the surge tank isconnected to the source of air under pressure; and (b) the valve can beopened, so as to permit liquid effluent to flow into the surge tank fromthe effluent source, when the surge tank is not connected to the sourceof air under pressure.
 8. The apparatus of claim 1, wherein the meansfor inhibiting the flow of liquid effluent comprises a means forconstricting the flow of effluent from the sedimentary deposit tank tothe effluent destination.
 9. The apparatus of claim 8, wherein the meansfor constricting the flow of effluent from the sedimentary deposit tankto the effluent destination comprises a conduit connected to thesedimentary deposit tank outlet, suitable for connecting to the effluentdestination, and sized so as to constrict the flow of liquid effluent.10. The apparatus of claim the means for constricting the flow ofeffluent from the sedimentary deposit tank to the effluent destinationcomprises a throttle valve connected to the sedimentary deposit tankoutlet and suitable for connecting to the effluent destination, wherebythe flow of effluent can be adjusted by adjusting the throttle valve.11. The apparatus of claim 10, wherein the throttle valve is a needlevalve.
 12. The apparatus of claim 1, wherein the means for inhibitingthe flow of liquid effluent comprises a means for constricting the flowof effluent from the surge tank to the sedimentary deposit tank.
 13. Theapparatus of claim 8, wherein the means for constricting the flow ofeffluent from the surge tank to the sedimentary deposit tank comprises aconduit between the surge tank effluent outlet and the sedimentarydeposit tank inlet sized so as to constrict the flow of liquid effluent.14. The apparatus of claim 1, wherein the sedimentary deposit tankcomprises a series of baffle chambers separated by baffle walls, theseries of baffle chambers being structured and arranged so that theliquid effluent passes in sequence through the baffle chambers.
 15. Theapparatus of claim 1, wherein the means for receiving and applying thepressure differential is adapted for connecting the surge tank andsedimentary deposit tank in-line with a source of such pressuredifferential comprising a suction/vacuum pump system for use in a dentaloffice.
 16. The apparatus of claim 15, additionally comprising auxiliarymeans for removing mercury from the effluent, such auxiliary means beinginterposed between the effluent source and the effluent destination andcomprising one or more of the following: one or more suitable selectedfilters (including porous membranes) or traps past or through whichliquid, liquid/solid, or vapor effluent passes en route to the effluentdestination; one or more means for introducing into the effluent one ormore suitable selected chelating agents, coagulants, precipitants, orflocculants; and one or more suitable selected adsorbent materialsplaced in contact with the effluent.
 17. The apparatus of claim 1,wherein the means for receiving and applying the pressure differentialis adapted for connecting the surge tank and sedimentary deposit tankin-line with a source of such pressure differential comprising asuction/vacuum pump system for use in a dental office.
 18. The apparatusof claim 17, additionally comprising auxiliary means for removingmercury from the effluent, such auxiliary means being interposed betweenthe effluent source and the effluent destination and comprising one ormore of the following: one or more suitable selected filters (includingporous membranes) or traps past or through which liquid, liquid/solid,or vapor effluent passes en route to the effluent destination; one ormore means for introducing into the effluent one or more suitableselected chelating agents, coagulants, precipitants, or flocculants; andone or more suitable selected adsorbent materials placed in contact withthe effluent.
 19. The apparatus of claim 1, wherein the means forreceiving and applying a pressure differential comprises means forconnecting the surge tank and sedimentary deposit tank in-line to avacuum system, the vacuum system having in-line a suctioning deviceconnectable to the surge tank inlet for suctioning liquid effluent froma source of effluent and a vacuum pump capable of passing both gas andliquid and connectable to the sedimentary deposit tank outlet, theapparatus additionally including an air bypass conduit forinterconnecting the surge tank inlet with the sedimentary deposit tankoutlet in parallel with the in-line passage comprising the surge tankinlet, the surge tank, the surge tank outlet, the sedimentary deposittank inlet, the sedimentary deposit tank, and the sedimentary deposittank outlet; wherein (a) the surge tank and the bypass conduit areinterconnected so as to permit air entering the surge tank through thesurge tank inlet to pass out of the surge tank through the bypassconduit; and wherein, when the said connections and interconnections aremade and the vacuum pump is operating, (b) the pressure at thesuctioning device is higher than the pressure inside the surge tank andthe pressure inside the surge tank is higher than the pressure at thesedimentary deposit tank outlet, (c) the pressure differential betweenthe suctioning device and the surge tank causes air and liquid effluentdrawn into the suctioning device to flow into the surge tank via thesurge tank inlet; and (d) the pressure differential between the surgetank and the vacuum pump causes air to flow from the surge tank via theair bypass conduit to the vacuum pump, and liquid effluent to flow fromthe surge tank through the sedimentary deposit tank and out thesedimentary deposit tank outlet.